This invention generally relates to elevators. More particularly, this invention relates to braking devices for elevators.
Elevator systems typically include safety braking devices to protect against overspeed conditions. Conventionally, safety governors include a governor wheel located near the top of a hoistway, a governor rope and a tension pulley in a hoistway pit. The governor rope is connected to a mechanical linkage that is supported on the elevator car. In the event of an overspeed condition, the governor wheel stops rotating. This prevents further movement of the governor rope. Any further movement of the elevator car causes the linkage to be pulled upon by the stationary governor rope. Movement of the linkage activates safety braking devices in a known manner.
While such arrangements have proven useful, they are not without limitations. One drawback associated with conventional arrangements is that the governor rope is typically provided on one side of an elevator car such that a linkage is utilized to activate safety braking devices on both sides of the car.
Recent developments in elevator systems make it desirable to introduce new approaches. For example, conventional safety governor arrangements take up space in the hoistway because there must be a certain amount of space allocated to the governor wheel and the tension pulley, for example. The use of machine roomless elevators includes the desire to reduce hoistway dimensions as much as possible. This requires reducing the volume occupied by the various components in the hoistway as much as possible. At the same time, the safety functions provided by an overspeed governor should be maintained.
One improvement in this area is disclosed in U.S. Pat. No. 6,161,653, which discloses a ropeless governor mechanism for an elevator car that relies upon electrically-based activation of the safety device.
This invention provides another arrangement for preventing undesired movement of an elevator car.